Wednesday, April 20, 2011

Pack Assembly

I've spent two sessions now with the battery tab welder. The first was to create 5 cell groups. I then had to take the 5 cell groups and bend the tabs so the cells were end to end. I used a PVC pipe from Home Depot which was a slight oversize on the cells to assist in aligning them when bending the tabs. This 5 cell group was then wrapped in a tough 5 mil heat shrink to form a "stick". I assembled all these sticks (112 of them) into 4 stick groups. Each of the 4 stick groups has two tabs welded to the bottom, and 3 on the top. It was difficult to find, but I finally found a place to get 10 mil nickel tabs (and did not force me to order 5kg worth). Previously, I could only get 5 mil tabs which I think are a bit small for the top and bottom tabs as they see much harsher physical stresses. I checked each of the groups with a voltmeter and all were within 0.2 volts of each other. This means I have no dead cells (opens or shorts). I did build 2 extra 4 stick groups in case I need to swap them out and I will keep them as a future spare parts. What remains is to install the 2 new Battery Management Boards, install the removable fuse, replace the cover (may think about replacing the fans as some point as they do not move much air) and test the packs in the Twike. I hope to be back on the road soon (and just in time as gas heads for $4/gallon). Expected range will be 30 to 40 miles per charge. I might think about building a mount for my third pack as well as the car supports it (program BMS to bat3 and plug it in). I'm concerned that packs of mixed capacity might cause the charger some problems but maybe not as it can open the charge relay on a per pack basis. I'll leave that to a future project.

1 comment:

The Thonnings Family said...

Hey Phil, you wouldn't happen to know any Twike owners near Ohio? I'm a teacher near Cleveland. We do a Junior Solar Sprint project with all of our 6th graders. On race day, we like to get displays of alternative vehicles for the kids to see. I've always wanted to get a hold of a twike owner to see if they could showcase it. Thanks. Kurt thonnings@wlake.org